While the simplest models of inflation predict gaussian adiabatic
perturbations, many models are known which violate either or both of
these conditions. Consequently there is no critical test of inflation
which can be simply stated. Nevertheless, it is clear that these could
lead to tests of the inflationary paradigm. For example, as far as
inflation is concerned, there is good nongaussianity and bad
nongaussianity. For example, if line discontinuities are seen in the
microwave background, it would be futile to try and explain them using
inflation rather than cosmic strings. On the other hand, nongaussianity
with a chi-squared distribution is very easy to generate in inflation
models; one only has to arrange that the leading contribution to the
density comes from the square of a scalar field
perturbation. Indeed, in isocurvature inflation models, it appears at
least as easy to arrange chi-squared statistics as it is to arrange
gaussian ones
[19].

Inflation may also be able to explain nongaussian perturbations of a
`bubbly' nature, by attributing the bubbles to a phase transition
bringing inflation to an end. The simplest models of this type have
already been excluded, but more complicated ones may still be viable.